1. Field of the Invention
The present invention relates to a semiconductor device and a printed board on which the semiconductor device is mounted, and particularly relates to technology of reducing radiation noise of the semiconductor device.
2. Description of the Related Art
Due to miniaturization in semiconductor process technology, the scale of circuits mounted on semiconductor chips has been dramatically increased. Accordingly, it is possible to mount many functional portions on one chip. In order to realize this, it is necessary to increase the number of external lead terminals of a semiconductor package, to further narrow the pitch between terminals, and to also narrow the width of inner leads constituted inside the semiconductor package. Japanese Patent Laid-Open No. 5-055305 proposes using connection terminals closest to the four corners of an LSI chip as connection terminals for a power source circuit, and causing the length of conductor leads connected to these terminals to be the shortest among the lengths of a plurality of conductor leads with which the mounting package is provided.
According to Japanese Patent Laid-Open No. 5-055305, the length of the conductor leads connected to the connection terminals close to the four corners needs to be set shorter than the length of conductor leads connected to connection terminals that are farther from the four corners (that is, in the center portion of each side of the package). Therefore, the arrangement direction of the tip portions of the inner leads needs to form a 30 to 45-degree angle relative to the arrangement direction of the outer leads. However, if the size of a semiconductor package is large compared to the area of the semiconductor chip (for example, the case where one side of a 256-pin QFP package is about 30 mm, and one side of a semiconductor chip is about 7 mm), the effect of reducing the length of inner leads decreases. Further, since the width of the individual inner leads and the interval between the inner leads are extremely narrow, high frequency coupling due to parasitic capacitance components formed between neighboring inner leads and noise interference due to mutual inductance may occur.